mirror of
https://github.com/moparisthebest/curl
synced 2024-12-22 16:18:48 -05:00
106 lines
4.8 KiB
Groff
106 lines
4.8 KiB
Groff
.\" $Id$
|
|
.\"
|
|
.TH libcurl 3 "19 March 2002" "libcurl 7.9.6" "libcurl overview"
|
|
.SH NAME
|
|
libcurl \- client-side URL transfers
|
|
.SH DESCRIPTION
|
|
This is an short overview on how to use libcurl in your C programs. There are
|
|
specific man pages for each function mentioned in here. There are also the
|
|
\fIlibcurl-easy(3)\fP man page, the \fIlibcurl-multi(3)\fP man page, the
|
|
\fIlibcurl-share(3)\fP man page and the \fIlibcurl-tutorial(3)\fP man page for
|
|
in-depth understanding on how to program with libcurl.
|
|
|
|
There are more than a twenty custom bindings available that bring libcurl
|
|
access to your favourite language. Look elsewhere for documentation on those.
|
|
|
|
All applications that use libcurl should call \fIcurl_global_init(3)\fP
|
|
exactly once before any libcurl function can be used. After all usage of
|
|
libcurl is complete, it \fBmust\fP call \fIcurl_global_cleanup(3)\fP. In
|
|
between those two calls, you can use libcurl as described below.
|
|
|
|
To transfer files, you always set up an "easy handle" using
|
|
\fIcurl_easy_init(3)\fP, but when you want the file(s) transferred you have
|
|
the option of using the "easy" interface, or the "multi" interface.
|
|
|
|
The easy interface is a synchronous interface with which you call
|
|
\fIcurl_easy_perform(3)\fP and let it perform the transfer. When it is
|
|
completed, the function return and you can continue. More details are found in
|
|
the \fIlibcurl-easy(3)\fP man page.
|
|
|
|
The multi interface on the other hand is an asynchronous interface, that you
|
|
call and that performs only a little piece of the transfer on each invoke. It
|
|
is perfect if you want to do things while the transfer is in progress, or
|
|
similar. The multi interface allows you to select() on libcurl action, and
|
|
even to easily download multiple files simultaneously using a single thread. See further deails in the \fIlibcurl-multi(3)\fP man page.
|
|
|
|
You can have multiple easy handles share certain data, even if they are used
|
|
in different threads. This magic is setup using the share interface, as
|
|
described in the \fIlibcurl-share(3)\fP man page.
|
|
|
|
There is also a series of other helpful functions to use, including these:
|
|
.RS
|
|
.IP curl_version_info()
|
|
gets detailed libcurl (and other used libraries) version info
|
|
.IP curl_getdate()
|
|
converts a date string to time_t
|
|
.IP curl_easy_getinfo()
|
|
get information about a performed transfer
|
|
.IP curl_formadd()
|
|
helps building an HTTP form POST
|
|
.IP curl_formfree()
|
|
free a list built with \fIcurl_formadd(3)\fP
|
|
.IP curl_slist_append()
|
|
builds a linked list
|
|
.IP curl_slist_free_all()
|
|
frees a whole curl_slist
|
|
.RE
|
|
|
|
.SH "LINKING WITH LIBCURL"
|
|
On unix-like machines, there's a tool named curl-config that gets installed
|
|
with the rest of the curl stuff when 'make install' is performed.
|
|
|
|
curl-config is added to make it easier for applications to link with libcurl
|
|
and developers to learn about libcurl and how to use it.
|
|
|
|
Run 'curl-config --libs' to get the (additional) linker options you need to
|
|
link with the particular version of libcurl you've installed. See the
|
|
\fIcurl-config(1)\fP man page for further details.
|
|
|
|
Unix-like operating system that ship libcurl as part of their distributions
|
|
often don't provide the curl-config tool, but simply install the library and
|
|
headers in the common path for this purpose.
|
|
|
|
.SH "LIBCURL SYMBOL NAMES"
|
|
All public functions in the libcurl interface are prefixed with 'curl_' (with
|
|
a lowercase c). You can find other functions in the library source code, but
|
|
other prefixes indicate that the functions are private and may change without
|
|
further notice in the next release.
|
|
|
|
Only use documented functions and functionality!
|
|
.SH "PORTABILITY"
|
|
libcurl works
|
|
.B exactly
|
|
the same, on any of the platforms it compiles and builds on.
|
|
.SH "THREADS"
|
|
Never ever call curl-functions simultaneously using the same handle from
|
|
several threads. libcurl is thread-safe and can be used in any number of
|
|
threads, but you must use separate curl handles if you want to use libcurl in
|
|
more than one thread simultaneously.
|
|
.SH "PERSISTENT CONNECTIONS"
|
|
Persistent connections means that libcurl can re-use the same connection for
|
|
several transfers, if the conditions are right.
|
|
|
|
libcurl will \fBalways\fP attempt to use persistent connections. Whenever you
|
|
use \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP, libcurl will
|
|
attempt to use an existing connection to do the transfer, and if none exists
|
|
it'll open a new one that will be subject for re-use on a possible following
|
|
call to \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP.
|
|
|
|
To allow libcurl to take full advantage of persistent connections, you should
|
|
do as many of your file transfers as possible using the same curl handle. When
|
|
you call \fIcurl_easy_cleanup(3)\fP, all the possibly open connections held by
|
|
libcurl will be closed and forgotten.
|
|
|
|
Note that the options set with \fIcurl_easy_setopt(3)\fP will be used in on
|
|
every repeated \fIcurl_easy_perform(3)\fP call.
|